native_apps_blog_canny_plc.cpp

/**
 * Gautam Muralidhar,Srivatsan Ramanujam Oct 2014
 * PL/C function for invoking Canny's Edge Detection from OpenCV
 **/
extern "C" {
    #include <postgres.h>
    #include <fmgr.h>
    #include <utils/array.h>
    #include <utils/builtins.h>
    #include <catalog/pg_type.h>
    #include <string>
    #include <vector>
    #include <stdlib.h>
    #include <stdint.h>

    #ifdef PG_MODULE_MAGIC
    PG_MODULE_MAGIC;
    #endif

    // Postgres interface for getImgSizeFromByteStream
    PG_FUNCTION_INFO_V1(get_imgsize);
    Datum get_imgsize(PG_FUNCTION_ARGS){
        if (PG_ARGISNULL(0)){
             ereport(ERROR, (errmsg("Null arrays not accepted")));
        }
        // Collect the input image byte stream as C string
        char* cstr = TextDatumGetCString(PG_GETARG_DATUM(0));
        string str(cstr);
        vector<string> tokens;
        // Tokenize the string on “,” and collect the tokens, which represent individual bytes of the image
        Tokenize(str, tokens, ",");
        vector<int8_t> src;
        for (int i = 0; i < tokens.size(); i++) {
            const char* tk = tokens[i].c_str();
            int bt = atoi(tk);
            src.push_back(bt);
        }
        // Call the internal getImgSizeFromByteStream function
        uint* imgSize = getImgSizeFromByteStream(src);
        Datum* imgSizeArray = (Datum*)palloc(sizeof(Datum) * 2);
        for (int i = 0; i < 2; i++) {
            imgSizeArray[i] = imgSize[i];
        }
        // Construct the array to be returned back to the database client
        ArrayType *res = construct_array(imgSizeArray, 2, INT4OID, 4, true, 'i');
        PG_RETURN_ARRAYTYPE_P(res); 
    }

    // Postgres interface for edgeDetectionFromByteStream
    PG_FUNCTION_INFO_V1(canny_plc);
    Datum canny_plc(PG_FUNCTION_ARGS){
        if (PG_ARGISNULL(0)){
             ereport(ERROR, (errmsg("Null arrays not accepted")));
        }
        // Collect the input image byte stream as C string
        char* cstr = TextDatumGetCString(PG_GETARG_DATUM(0));
        string str(cstr);
        vector<string> tokens;
        // Tokenize the string on “,” and collect the tokens, which represent individual bytes of the image
        Tokenize(str, tokens, ",");
        vector<int8_t> src;
        for (int i = 0; i < tokens.size(); i++) {
            const char* tk = tokens[i].c_str();
            int bt = atoi(tk);
            src.push_back(bt);
        }
        // Call the internal getImgSizeFromByteStream function
        uint* imgSize = getImgSizeFromByteStream(src);
        uint* edge_result = new uint[imgSize[0]*imgSize[1]];

        // Call the internal edgeDetectionFromByteStream function
        bool success = edgeDetectionFromByteStream(src, edge_result);
        if (success) {
            Datum* imgSizeArray = (Datum*)palloc(sizeof(Datum) * imgSize[0]*imgSize[1]);
            for (int i = 0; i < imgSize[0]*imgSize[1]; i++) {
                imgSizeArray[i] = edge_result[i];
            }

            // Construct the array to be returned back to the database client
            ArrayType *res = construct_array(imgSizeArray,
                imgSize[0]*imgSize[1], INT4OID, 4, true, 'i');
            PG_RETURN_ARRAYTYPE_P(res);
        } else {
            ereport(ERROR, (errmsg("Edge detection failed")));
        }
    }
}